Search results for "control systems"
showing 10 items of 590 documents
Sequential design of multioverlapping controllers for structural vibration control of tall buildings under seismic excitation
2012
In this article, a computationally effective strategy to obtain multioverlapping controllers via the inclusion principle is applied to design a state-feedback multioverlapping linear-quadratic regulator controller for a 20-story building. The proposed semidecentralized controller only requires state information of neighboring stories to compute the corresponding control actions. This particular information exchange configuration allows introducing a dramatic reduction in the transmission range required for a wireless implementation of the communications system. More specifically, just a one-story transmission range is required by the proposed multioverlapping controller, while a full-buildi…
DSC: software tool for simulation-based design of control strategies applied to wastewater treatment plants.
2011
This paper presents a computer tool called DSC (Simulation based Controllers Design) that enables an easy design of control systems and strategies applied to wastewater treatment plants. Although the control systems are developed and evaluated by simulation, this tool aims to facilitate the direct implementation of the designed control system to the PC of the full-scale WWTP (wastewater treatment plants). The designed control system can be programmed in a dedicated control application and can be connected to either the simulation software or the SCADA of the plant. To this end, the developed DSC incorporates an OPC server (OLE for process control) which facilitates an open-standard communic…
DEPENDENCE OF MACHINING SIMULATION EFFECTIVENESS ON MATERIAL AND FRICTION MODELLING
2008
Numerical simulation of cutting processes is still a very difficult matter, although some relevant geometrical simplifications and high-performance codes are used. A large number of technical papers have been focused on the predictive capability of the codes: nevertheless the prediction quality is not very satisfactory if the problem is analyzed in a wide sense. In this paper the simple orthogonal cutting process of a plain-carbon steel is investigated taking into account different process conditions (cutting speed and feed rate). Furthermore, four material constitutive equations and three friction models were implemented and a sensitivity analysis was carried out comparing the numerical pr…
Criticality and sensitivity analysis of the components of a system
2000
Abstract In the design of complex systems there is a great interest to know the relative importance of each of their elements. In this paper, we define a new method for measuring the relative importance of each element of the system. We have to specify that this paper concerns only non-repairable systems and components. We present a way of calculating the criticality of each component for a complex system no matter what the random distribution of the life of the component is. The paper also demonstrates a simple way of calculating how the system life improves when the life of a component is improved.
Life cycle assessment of Italian citrus-based products. Sensitivity analysis and improvement scenarios
2009
Though many studies concern the agro-food sector in the EU and Italy, and its environmental impacts, literature is quite lacking in works regarding LCA application on citrus products. This paper represents one of the first studies on the environmental impacts of citrus products in order to suggest feasible strategies and actions to improve their environmental performance. In particular, it is part of a research aimed to estimate environmental burdens associated with the production of the following citrus-based products: essential oil, natural juice and concentrated juice from oranges and lemons. The life cycle assessment of these products, published in a previous paper, had highlighted sign…
Variance-based sensitivity analysis for wastewater treatment plant modelling.
2014
Global sensitivity analysis (GSA) is a valuable tool to support the use of mathematical models that characterise technical or natural systems. In the field of wastewater modelling, most of the recent applications of GSA use either regression-based methods, which require close to linear relationships between the model outputs and model factors, or screening methods, which only yield qualitative results. However, due to the characteristics of membrane bioreactors (MBR) (non-linear kinetics, complexity, etc.) there is an interest to adequately quantify the effects of non-linearity and interactions. This can be achieved with variance-based sensitivity analysis methods. In this paper, the Extend…
Global sensitivity analysis in wastewater applications: A comprehensive comparison of different methods
2013
Three global sensitivity analysis (GSA) methods are applied and compared to assess the most relevant processes occurring in wastewater treatment systems. In particular, the Standardised Regression Coefficients, Morris Screening and Extended-FAST methods are applied to a complex integrated membrane bioreactor (MBR) model considering 21 model outputs and 79 model factors. The three methods are applied with numerical settings as suggested in literature. The main objective considered is to classify important factors (factors prioritisation) as well as non-influential factors (factors fixing). The performance is assessed by comparing the most reliable method (Extended-FAST), by means of proposed…
Global sensitivity analysis of a filtration model for submerged anaerobic membrane bioreactors (AnMBR)
2014
The results of a global sensitivity analysis of a filtration model for submerged anaerobic MBRs (AnMBRs) are assessed in this paper. This study aimed to (1) identify the less- (or non-) influential factors of the model in order to facilitate model calibration and (2) validate the modelling approach (i.e. to determine the need for each of the proposed factors to be included in the model). The sensitivity analysis was conducted using a revised version of the Morris screening method. The dynamic simulations were conducted using long-term data obtained from an AnMBR plant fitted with industrial-scale hollow-fibre membranes. Of the 14 factors in the model, six were identified as influential, i.e…
A polynomial algorithm solving a special class of hybrid optimal control problems
2006
Hybrid optimal control problems are, in general, difficult to solve. A current research goal is to isolate those problems that lead to tractable solutions [5]. In this paper, we identify a special class of hybrid optimal control problems which are easy to solve. We do this by using a paradigm borrowed from the Operations Research field. As main result, we present a solution algorithm that converges to the exact solution in polynomial time. Our approach consists in approximating the hybrid optimal control problem via an integer-linear programming reformulation. The integer-linear programming problem is a Set-covering one with a totally unimodular constraint matrix and therefore solving the S…
ECONOMIC-STATISTICAL DESIGN APPROACH FOR A VSSI X-BAR CHART CONSIDERING TAGUCHI LOSS FUNCTION AND RANDOM PROCESS SHIFTS
2014
Economic design approaches of control charts are commonly based on the assumption that various cost parameters values and the occurrence risk of assignable causes have to be a priori known with precision. However, in real operative contexts, such parameters can be really difficult to accurately estimate, especially considering costs arising from out-of-control conditions of the process. As consequence, pure economic design approaches can involve chart schemes with low statistical performance. To overcome such limitation, it is herein proposed a multi-objective economic-statistical design approach for an adaptive X-bar chart. In particular, such approach aims at the minimization of both the…